1. Field of the Invention
The present invention is directed to a stator wheel for a hydrodynamic torque converter comprising a stator wheel hub arrangement and a plurality of stator wheel blades arranged successively in the circumferential direction on the stator wheel hub arrangement. Each stator wheel blade has a radial inner flow-around profile area and a radial outer flow-around profile area and the flow-around profile in the radial outer flow-around profile area differs from the flow-around profile in the radial inner flow-around profile area.
2. Description of the Related Art
Hydrodynamic torque converters are generally used for transmitting torque in drivetrains of motor vehicles, especially motor vehicles with an automatic transmission, and use the fluid circulating within the torque converter to transmit torque between an impeller wheel and a turbine wheel of the torque converter. The flow of fluid exiting the turbine wheel is conducted into the impeller wheel via a stator wheel. This type of torque converter must be capable of performing the torque transmission coupling function or converter function over a wide range of operating states of a drive system. A high starting conversion is required particularly in the starting range in which the turbine wheel is initially at a standstill and only the impeller wheel is driven by the engine. However, a very high efficiency is required in the normal driving state in which the ratio of the turbine speed to the impeller speed is in a range of greater than 0.8. The different components used in a torque converter, in particular the turbine, impeller and stator, may have configurations which are adapted to the respective requirements, especially in the area of their respective blades. However, since the torque conversion on the one hand and the torque transmission without conversion on the other hand require different blade geometries to achieve optimum function in each particular case, compromises must be made so that the blades in torque converters have acceptable characteristics for both the starting range and normal driving operation. Accordingly, it is known, for example, to construct the stator wheel blades in such a way that they have a blade flow-around profile designed for the starting range in a radial inner area and a flow-around profile designed for normal driving operation or continuous operation in the radial outer area. A continuous transition of the profile takes place between the radial inside and radial outside of the stator wheel. The final result of this compromise is that the torque converter has no optimum characteristic for virtually any operating state.
A prior art torque converter is disclosed in EP 0 846 894 A2 in which the stator wheel blades are divided into a radial inner area and a radial outer area. In the radial inner area, the blades have an inner profile which is optimized essentially for the starting operation requirements. This inner profile extends approximately up to the radial longitudinal center of the blades and passes, via a step, into an outer flow-around profile which is designed for continuous operation in the radial outer area. However, unwanted flow mixtures occur at the step between the inner profile and the outer profile.